Immediate effects of photobiomodulation with low-level laser followed by the voiced tongue trill technique in women with behavioral dysphonia.
Viviane Souza Bicalho Bacelete, Andréa Rodrigues Motta, Elisa Meiti Ribeiro Lin Plec and 1 others
Adding infrared laser before a 5-minute tongue trill exercise did not improve voice quality, acoustics, or perceived effort more than the exercise alone in 30 women with behavioral dysphonia.
The one between-group difference was laryngeal appearance on video (60% vs 13.3% improved).
Key findings
1No significant between-group differences were found in auditory-perceptual voice quality (sustained vowel or continuous speech), acoustic and aerodynamic measures, or self-perceived phonatory effort after the intervention.
2The placebo-laser group (which received only the tongue trill exercise) also showed significant within-group improvements: continuous speech vocal deviation decreased (p = 0.047), and jitter and PPQ both decreased (p = 0.025 and p = 0.033), indicating the exercise itself produced effects.
3The only significant between-group difference was in the visual-perceptual evaluation of high-speed laryngeal video: 9 of 15 (60%) in the laser group showed improved glottal closure, phase symmetry, mucosal wave, or cycle periodicity, versus 2 of 15 (13.3%) in the placebo group (p = 0.017).
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What it does not show
Only 30 participants (15 per group), which the authors repeatedly note limited statistical power to detect small or moderate differences between the two conditions. Single session with immediate post-intervention assessment only; no follow-up, so nothing is known about whether any effect lasts beyond the session. Convenience sample recruited from one university clinic in Brazil; all participants were women, limiting generalisability to men or to other populations. The researcher applying the laser was not blinded — they had to operate the device differently for each group (emitting light versus beeping only) — so performance bias is possible. No single primary outcome was pre-specified; four outcome domains were reported, increasing the chance that one reaches significance by chance. The placebo group also showed significant within-group improvements, making it difficult to attribute any change in the laser group specifically to the light rather than to the exercise or to assessment effects.
Declared interests
Funded by two Brazilian government bodies: CNPq (Grant No. 309108/2019-5) and CAPES (Finance Code 001). No industry funding, no device manufacturer involvement, and no conflicts of interest were declared.
The easy way to misread this
Do not read the 60%-versus-13.3% laryngeal-video improvement as proof that laser treats dysphonia. Both groups received the same tongue trill exercise, and the placebo group also showed significant gains in speech quality and vocal periodicity. The researcher was not blinded (they operated the device differently for each group), the sample was 30 women in a single session, and no primary outcome was pre-specified. The one between-group difference is a small, single-session signal, not evidence to add a laser step to a vocal-exercise protocol.
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